Switch actuating mechanism



y 5, 195 8 R. G. STAPLES, JR 2,843,692

SWITCH ACTUATING MECHANISM Filed Feb. 27, 1957 VIIIlIIII/IIIIII/fl SWITCH ACTUATING NIECHANISM Robert G. Staples, In, North Wales, Pa., assignor to Link-Belt Company, a corporation of Illinois Application February 27, 1957, Serial No. 642,761

8 Claims. (Cl. ZOO-85) This invention relates to actuating mechanism and deals more particularly with mechanism for actuating limit switches, or the like.

The primary object of this invention is to provide an actuating mechanism for limit switches or the like, which is operated by the weight of an object traveling over a movable member of the mechanism.

Another object of this invention is to provide an actuating mechanism of the aforementioned type which may be adapted for operation by a minimum of pressure on and a minimum motion of the movable member of the mechanism, and in which the operation is independent of the direction in which the traveling object approaches the said movable member.

A further object of the present invention is to provide an actuating mechanism which is rugged, easily serviced, of a simple low cost construction, and capable of adaptation for use in connection with relatively large and heavy traveling objects.

A more detailed object of the present invention is to provide a gravity biased actuating mechanism for limit switches, or the like, employing no springs and having few moving parts.

Other objects and advantages of the invention will be apparent during the course of the following description.

In the accompanying drawings forming a part of this specification and in which like reference characters are employed to designate like parts throughout the same.

Figure 1 is a vertical sectional view of an actuating mechanism embodying the invention, and

Figure 2 is a partly horizontal sectional view and a partly top plan view taken on line 2-2 of Fig. 1.

In the drawings, wherein for the purpose of illustration is shown a preferred embodiment of this invention, reference character 11 designates a metal frame, or housing, for carrying the various elements of the actuating mechanism, which may be fabricated from flat stock pieces interconnected by welding or other fastening methods. In the present instance, the frame is shown to be made up of a top plate 12, two side pieces 13, an interiorly positioned brace plate 14 and a bottom plate 15 which serves as a mounting bracket for the frame and is accordingly provided with holes for receiving bolts 16 used to attach the frame to an underlying support 17. If desired, the overall height of the frame may be varied by the use of shim material 18 interposed between the plate 15 and the support 17.

In the top part of the frame is carried a movable member, indicated generally by the reference character 19, designed to be operated on by the weight of an object moving over its top from any direction, and composed of a plunger 20 slidably mounted for vertical reciprocation within a sleeve 21 rigidly connected to the frame 11. The top portion of the plunger 20 is rounded to produce a spherical surface 22. In use, the mechanism is placed so that with the plunger in its normal ready position this spherical surface 22 protrudes v 1 2,843,692 Patented July 15, 1958 "ice above the path followed by the bottom of a moving object that is approaching the actuating mechanism.

This is illustrated clearly in Figure 1 wherein there is shown an imaginary object W approaching the actuating mechanism 19 along a bottom path A. The spherical surface 22 alone protrudes above the bottom path A, and is comparatively small in comparison with the size of the object W. It is apparent from this figure that as the object W moves over the spherical top surface, the plunger will be driven downwardly.

Preferably, the spherical surface 22 is movable and in such a manner that a rolling action, rather than a sliding action, occurs between the actuating element 19 and the object W. The provision of such a rolling action greatly reduces wear, minimizes the force required to move the object W over the plunger 20, and makes possible a convenient method of lubrication. In the present instance a rolling action is attained by constructing the plunger 20 from a cylinder 24 in the head of which is carried a captive metal ball 25. Interiorly the cylinder is formed with a parti-spherical shoulder 26 closely conforming to the surface of the ball 25 and terminating in an opening 27 through which a portion of the ball protrudes to define the spherical top surface. A bottom plug 29, held in place in the cylinder 24 by lock screws 30, bears against the bottom of the ball 25 and holds it in running contact with the parti-sphreical shoulder 26. Lubricating between the cylinder 24 and the ball 25 is facilitated by the use of a conventional grease fitting 31 mounted in the sleeve 21 and communicating with grease grooves 32 formed in the exterior surface of the cylinder 24. Holes 34 in the wall of the cylinder 24 permit the entry of grease into the interior of the cylinder 24 to fill the empty space therein, this space acting as a grease reservoir for the ball 25. Thus, the contacts between the ball and the cylinder, and between the ball and the moving object, are lubricated by grease picked up by the rolling ball as it moves through the reservoir.

To prevent the cylinder 24 from protruding above the bottom path A of the object W, a stop is provided to limit the upward travel of the plunger 20. In the present instance, this stop is provided by forming an outstanding flange 35 on the bottom plug 29 which engages the bottom of the sleeve 21 when the plunger 20 is in its uppermost position.

An electrical switch 36, controlled by an operating arm 38 fixed to a rotatable operating shaft 39, is mounted on the brace plate 14 by means of bolts 40. This switch is supplied with current by a conduit 41 containing electrical conductors 42. The operating lever 38 is counterbalanced by a counterweight 44, placed oppositely to its lever in respect to the shaft 39, which is slightly less than needed to completely balance the arm 38, so that the arm is slightly biased downwardly and capable of being lifted into an elevated position by a relatively small force. For purposes of discussion, it is herein assumed that with the operating arm 38 in its lower position, that is, the position normally assumed by it under the action of the gravity bias, the switch 36 is closed, and that when the arm 38 is in its lifted or elevated position the switch 36 is open.

In Fig. l the solid lines indicate the lower position of the arm 38 corresponding to a closed switch, while the broken lines represent the raised position of the arm 38 corresponding to an open position of the switch. It will be appreciated, however, that the two arm positions indicated do not represent the point at which the switch opens on the upward travel of the arm and the point at which the switch closes during the downward travel of the arm. These points actually lie somewhere within the range of travel indicated, and, as is here- 3 inafter described, an adjustment is provided for shifting the range of travel so that the switch points fall properly therewithin.

A basic part of the present invention is the provision of means for operatively connecting the movable member 19 with the switch 36 so that the latter is operated in response to the reciprocating movement of the movable member. This means is shown to comprise a rockable lever, indicated generally by the reference character 45, which by its rocking action transforms the downward movement of the actuating member 19 into an upward lifting of the operating arm 33. As best shown in Fig. 2, the rockable lever 45, in the present instance, is rotatably mounted on a stationary shaft 46 mounted on the side walls 13 of the frame 11, by means of side collars 48 rigidly fixed to the side walls, and secured against rotation by set screws 45 in the collars 48.

The lever 45 is shown to consist of a bushing 50, a first lever 51 rigidly connected to one end of the bushing and cooperating with the actuating member 19, and an oppositely directed second lever 52 rigidly connected to the other end of the bushing cooperating with the operating arm 38 of the switch 36. For obvious reasons the bushing 50 is preferably of a conventional permanently lubricated type. The lever 45 is properly secured and positioned on the shaft 46 by means of a retaining collar 54 clamped to the shaft 46 and a washer 55 interposed between the lever 45 and the side collar 48.

The first arm 51 of the lever 45 is provided with a roller 56 on its free end positioned to engage the bottom of the plunger 20 at an essentially centrally located point, and the second arm 52 is provided with a flat cam surface 58. The free end of the operating lever 38 is provided with a roller 59 positioned so as to rest on the cam surface 58. Both of the rollers 56 and 59 are employed in order to provide low friction rolling contacts serving to reduce the amount of force needed to operate the mechanism. The fiat cam surface 58 is obtained by attaching to the second arm 52 a cam member 64 having a downwardly extending side piece 61 and a bottom piece 62 disposed normally to the side piece 61 and inclined in respect to the longitudinal axis of the arm 52. The top surface of the bottom piece 62 provides the flat cam surface 58 on which the operating lever roller 59 rests.

The cam member 60 is secured to the arm 52 by means of bolts 63 passing through holes in the side piece registering with spaced slots 64 in the arm allowing the cam member to be adjustably positioned along the longitudinal axis of the cam. It will be noted that, by virtue of the inclined relationship between the flat surface 58 and the longitudinal axis of the arm 52, longitudinal positioning of the cam member 60 on the arm effects an adjustment for shifting the range of travel of the operating lever 38. Moving the cam member outward along the arm 52 shifts the travel range of the lever 38 upwardly, and moving the cam member inwardly along the arm 52 shifts the range of travel to a lower position. By this adjustment the range of the operating lever 33 is easily set for proper action of the switch 36.

In order to hold the actuating member 19 in its ready upward position, the lever 45 is counterbalanced so as to exert a gravity induced force on the movable member 19 tending to urge it upwardly. In the present instance this counterbalancing is conveniently accomplished by making the bottom piece 62 of the camming member 661 of relatively heavy material of sufficient weight to overcome the combined weight of the actuating member 19 and the arm 51. It will be apparent that the degree of force necessarily exerted by the object W on the member 19 to produce a switching action is dependent on the amount of counterbalancing Weight attached to the arm 52 as Well as the relative lengths of the arms 51 and 52 which determine the mechanical advantage of the lever 45. Assuming a fixed mechanical advantage, the actuating mechanism may be made sensitive to relatively light objects moving over it, by providing, on the arm 52, only a little more weight than necessary to completely balance the system, while by employing an excessive amount of Weight on the arm 52 the actuating mechanism may be made insensitive to lighter articles passing over it and sensitive only to objects exceeding a preselected weight. Similar results may of course be obtained by varying the relative lengths of the lever arms while holding the counterbalancing weight fixed.

The mode of operation of this mechanism may be briefly described. In its normal ready position, the actu ating plunger 20 is held in its uppermost position by a gravity induced force exerted on its bottom through the roller 56. In this position of the actuating plunger its spherical top portion 22 is disposed within the bottom path of objects moved toward it. As the object contacts the spherical surface it rolls or slides over it with the result that the plunger is driven downwardly by the weight of the object, into the position shown in broken lines in Fig. 1. This downward movement of the plunger in turn rocks the lever 45 which lifts the operating lever 38, as shown by the broken lines of Fig. 1, to actuate the switch 36. After the object is removed from the top of the plunger, gravity forces return the plunger, the lever 45 and the operating lever to their normal ready position, with the switch 36 being deactivated as the operating arm falls back to its normal position.

It is to be understood that the form of this invention herewith shown and described is to be taken as preferred example of the same, and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the subjoined claims.

Having thus described the invention, 1 claim,

1. An actuating mechanism, comprising a switch, said switch including an operating lever for controlling its actuation, a reciprocal plunger formed with a spherical top portion and adapted to be reciprocated by objects passing over said top portion, and a pivoted lever having a first arm cooperating with said operating lever and a second arm cooperating with said plunger so as to move said operating lever and thereby actuate said switch in response to the reciprocating movement of said plunger.

2. An actuating mechanism comprising a frame, a switch mounted on said frame and having an operating lever, an upwardly biased actuating plunger slidably mounted on said frame for limited vertically reciprocating movement, a spherical top portion on said plunger, said top portion comprising a captive rollable ball carried in the head of said plunger and protruding thereform, and lever means for moving said operating lever in response to a reciprocating movement of said plunger, said lever means including a first arm operatively contacting said plunger and a second arm operatively contacting said operating lever.

3. An actuating mechanism, comprising a frame, an actuating plunger slidably mounted on said frame for vertically reciprocating movement, a spherical top surface provided on said plunger by a captive rollable ball carried in the head of said plunger, stop means for limiting the upward travel of said plunger, a switch mounts-Ll on said frame and having an operating lever, and a second lever pivotally mounted in said frame cooperating with said plunger and said operating lever to move said operating lever in response to a movement of said plunger, said second lever including a first arm operatively con tacting the bottom of said plunger, a second arm operatively contacting said operating lever, and a Wei ht fastened to one of said arms to gravity bias said Pill in an upward direction.

4. An actuating mechanism, comprising a frame, a vertical sleeve mounted on said frame, a cylinder slidably carried in said sleeve, a ball disposed within said cylinder, a parti-spherical seat formed in the interior top pcr tion of said cylinder dimensioned to provide a running fit with said ball and to retain said ball within said cylinder while permitting a portion of the ball to protrude above the top of said cylinder, a plug in the bottom of said cylinder engaging the bottom of said ball and holding the latter against said seat, said plug also having an outstanding fiange dimensioned to engage said sleeve to limit the upward travel of said cylinder, a separate switch mechanism mounted on said frame, and means for actuating said switch mechanism in response to the up and down movement of said cylinder in said sleeve.

5. An actuating mechanism, comprising a frame, a slidable plunger vertically mounted in said frame, a captive ball rollably carried in the head of said plunger and partially projecting therefrom, a stop limiting the upward movement of said plunger, a switch mounted on said frame actuated by means of an operating lever biased downwardly, and means for lifting said operating lever and actuating said switch in response to a slight downward movement of said plunger, said means comprising a two-armed lever mounted for pivotal movement about an axis with its arms extending outwardly from said axis in essentially opposite directions, the first lever arm being so disposed as to bear with its free end against the bottom of said plunger and the second lever arm having mounted on its free end a cam formed with a flat surface positioned to engage and support said operating lever, said cam being of sufiicient weight to counterbalance the weight of the said plunger and bias the latter in an upward direction.

6. An actuating mechanism, comprising a switch, said switch including an operating lever, an upwardly biased slidable plunger adapted to be moved downward by an object moving over it, means for moving said operating lever to activate said switch in response to the up and down movement of said plunger, and means for adjustably shifting the travel range of said operating lever so as to obtain proper switching action of said switch.

7. An actuating mechanism as defined in claim 5 further characterized by said flat cam surface being at a fixed inclination with respect to the longitudinal axis of said second lever arm and said cam being adjustably positionable along the longitudinal axis of said second lever arm to shift the range of travel of said operating lever.

8. An actuating mechanism comprising a frame, a vertical sleeve mounted on said frame, a cylinder slidably carried in said sleeve, a ball disposed within said cylinder, a atti-spherical seat formed in the interior top portion of each cylinder dimensioned to provide a running fit with said ball and to retain said ball within said cylinder while mounting a portion of the ball to protrude above the top of said cylinder, a plug in the bottom of said cylinder engaging the bottom of said ball and holding the latter against said seat, said plug also having an outstanding flange dimensioned to engage said sleeve to limit the upward travel of said cylinder, and lever means movable by said cylinder for actuating a switch in response to the up and down movement of said cylinder in said sleeve.

References Cited in the file of this patent UNITED STATES PATENTS 911,943 Culver Feb. 9, 1909 2,350,063 Overby et al. May 30, 1944 2,494,819 Lane Jan. 17, 1950 2,684,413 Ripple July 20, 1954 

